JP6906931B2 - Image forming device - Google Patents

Description

The present invention relates to an electrophotographic image forming apparatus that forms an image using a liquid developer.

Conventionally, an electrostatic latent image formed on a photosensitive drum is developed into a toner image using a liquid developer containing a toner and a carrier liquid, and the developed toner image is primarily transferred to an intermediate transfer body, and then an intermediate transfer body is further developed. There is known an image forming apparatus that secondarily transfers a toner image transferred to a recording material to a recording material. In such an image forming apparatus, the toner image can be developed and transferred by forming a liquid layer of the carrier liquid on the photosensitive drum or the intermediate transfer body.

However, when the amount of the carrier liquid of the intermediate transfer material, that is, the liquid amount of the carrier liquid layer is larger than the appropriate amount, a fixing defect is likely to occur when fixing the toner image on the recording material. Therefore, conventionally, an image forming apparatus for removing excess carrier liquid from the carrier liquid layer has been proposed (Patent Document 1). In the apparatus described in Patent Document 1, excess carrier liquid is removed from the carrier liquid layer by a sweep roller that abuts on the photosensitive drum and rotates. However, at this time, if the amount of the carrier liquid layer is less than the appropriate amount and the carrier is insufficient, transfer failure occurs at the time of transferring the toner image due to the carrier shortage, so the liquid amount of the carrier liquid layer after removal is appropriate. Adjusted to quantity.

Further, although the image forming apparatus uses a dry developing agent instead of a liquid developing agent, a tandem type intermediate transfer type image forming apparatus in which a plurality of photosensitive drums are arranged side by side in the moving direction of the intermediate transfer belt has been conventionally proposed. (Patent Document 2). In this image forming apparatus, as an image forming mode, for example, a full color mode in which an image is formed using yellow, magenta, cyan, and black and a monochrome mode in which an image is formed using only black can be selectively executed. Then, in the full color mode, all the photosensitive drums are brought into contact with the intermediate transfer belt (hereinafter, also simply referred to as a belt), and in the monochrome mode, only the black photosensitive drums are brought into contact with the belt.

Japanese Unexamined Patent Publication No. 2003-91161 JP-A-2010-66452

Recently, there has been a demand to construct a tandem type image forming apparatus as described in Patent Document 2 in order to further reduce the size of an image forming apparatus using a liquid developer. However, in such a case, since all the photosensitive drums are in contact with the belt in the full color mode, excessive carriers in the carrier liquid layer are likely to occur. On the other hand, in the monochrome mode, since only the black photosensitive drum is in contact with the belt, a carrier shortage of the carrier liquid layer is likely to occur. Therefore, a device capable of removing the carrier liquid from the carrier liquid layer in the full color mode to eliminate the carrier excess and supplying the carrier liquid to the carrier liquid layer in the monochrome mode to solve the carrier shortage has been conventionally desired. No such device has been proposed.

The present invention has been made in view of the above problems, and provides an image forming apparatus capable of adjusting the amount of carrier liquid of an intermediate transfer belt according to an image forming mode by configuring a tandem type intermediate transfer method using a liquid developer. The purpose.

The image forming apparatus of the present invention includes a first image carrier on which an electrostatic latent image is formed, a second image carrier on which an electrostatic latent image is formed, and an electrostatic structure formed on the first image carrier. The first developing means for developing a latent image with a liquid developer containing a toner and a carrier liquid, and the electrostatic latent image formed on the second image carrier are liquid-developed with a toner and a carrier liquid. A second developing means for developing with an agent, an intermediate transfer body in which a toner image is primarily transferred with the movement of a carrier liquid from the first image carrier and the second image carrier, and an intermediate transfer body. A transfer means for secondarily transferring the primary transferred toner image to a recording material, and a first for primary transfer of the toner image with the movement of the carrier liquid from the first image carrier and the second image carrier to the intermediate transfer body. The mode and the first developing means are controlled so that the carrier liquid is not supplied from the first developing means to the first image carrier, and the toner is transferred from the second image carrier to the intermediate transfer body as well as the toner. A control means capable of selectively executing a second mode for primary transfer of an image, and the intermediate transfer to the downstream side of the second image carrier and upstream of the transfer means with respect to the moving direction of the intermediate transfer body. disposed opposite to the body, at least in the second mode, e Bei a supply means capable of supplying carrier liquid to the intermediate transfer member, said supply means capable of recovering the carrier liquid from the intermediate transfer member The control means can selectively execute a recovery mode in which the carrier liquid is recovered from the intermediate transfer body by the supply means and a supply mode in which the carrier liquid is supplied to the intermediate transfer body by the supply means. , Characterized by.

According to the present invention, since the carrier liquid can be supplied to the intermediate transfer body in the second mode and the amount of the carrier liquid in the intermediate transfer body can be adjusted, the carrier liquid in the intermediate transfer body is particularly likely to occur in the second mode. It is possible to solve the carrier shortage in which the amount of liquid is less than the appropriate amount.

The schematic diagram which shows the structure of the image forming apparatus of this embodiment. The cross-sectional view which shows the structure of the image forming part. The schematic which shows the liquid volume adjusting apparatus. The schematic diagram explaining the removal mode of the liquid amount adjusting apparatus. The control block diagram which shows the operation control system of a liquid amount adjusting apparatus. The flowchart which shows the liquid volume adjustment control. It is a figure explaining the liquid amount of a carrier liquid layer, (a) shows in the full color mode, (b) shows in the monochrome mode. The schematic diagram explaining the normal mode of the liquid amount adjusting apparatus. The schematic which shows another embodiment of the liquid volume adjusting apparatus.

[Image forming device]
The schematic configuration of the image forming apparatus of this embodiment will be described with reference to FIG. The image forming apparatus 100 shown in FIG. 1 is a tandem type intermediate transfer type full-color printer in which a plurality of image forming units PY, PM, PC, and PBk are arranged. In the present embodiment, the image forming portions PY to PBk are in series in a predetermined direction (moving direction) in which the intermediate transfer belt 91 as an endless intermediate transfer body moves, in the order of yellow, magenta, cyan, and black from the upstream side. Individually arranged.

The image forming apparatus 100 records a color image or a monochrome image formed according to image information from an external host device (not shown) such as a personal computer or an image reading device capable of communicating with the apparatus main body with a recording material S (for example, paper, etc.). It can be output to an OHP sheet, etc.). In the case of the present embodiment, a full-color mode in which a color image can be formed by using all the image forming units PY to PBk and a single-color mode in which a single-color image can be formed by using any one of the image forming units PY to PBk. Two image formation modes can be executed. In the present embodiment, as the monochromatic mode, a monochrome mode in which a monochrome image is formed by using only the black image forming unit PBk can be executed.

The image forming apparatus 100 generates a color-separated image signal according to a print signal sent from an external host apparatus, and each image forming unit PY to PBk forms a toner image of each color according to the image signal. In the case of the full color mode as the first mode, the image forming apparatus 100 continuously multiplex-transfers the toner images of each color formed by the image forming units PY to PBk onto the belt 91, and then multiple-transfers the plurality of colors from the belt 91. The toner image of the above is collectively transferred to the recording material S. On the other hand, in the case of the monochrome mode as the second mode, the image forming apparatus 100 transfers the black monochromatic toner image formed by the image forming unit PBk to the belt 91, and then transfers the monochromatic toner image transferred from the belt 91. Transfer to recording material S.

The recording material S on which the toner image is transferred is conveyed to the fixing device 13. When the recording material S is conveyed to the fixing device 13 and heated and pressurized or irradiated with ultraviolet rays, the toner image is fixed to the recording material S. The recording material S on which the toner image is fixed by the fixing device 13 is discharged to the outside of the machine body. In this way, a color image or a monochrome image is output to the recording material S.

[Image forming part]
As described above, the image forming portions PY to PBk that form the images of each color of yellow (Y), magenta (M), cyan (C), and black (Bk) will be described with reference to FIG. However, since the image forming units PY to PBk are configured to be the same except that the colors of the toners used in the developing devices 4Y to 4Bk are different, the image forming units PY to PBk are distinguished when no particular distinction is required. The explanation will be made by omitting Y, M, C, and Bk at the end of the reference numerals.

As shown in FIG. 2, in the image forming unit P, a charging device 2, an exposure device 3, a developing device 4, and a drum cleaning device 7 are arranged so as to surround the photosensitive drum 1. The photosensitive drum 1 as the first image carrier or the second image carrier is a photoconductor drum in which an amorphous silicon photosensitive layer is formed on the outer peripheral surface of a conductive aluminum cylinder. The photosensitive drum 1 is rotated in the direction of arrow R1 in the figure at a predetermined process speed by a motor or the like (not shown). The charging device 2 as the charging means is, for example, a scorotron type corona charger, which charges the surface of the photosensitive drum 1 to a uniform negative electrode dark potential. The exposure apparatus 3 generates laser light L, which is ON-OFF modulated from scanning line image data obtained by developing separated color images of each color, from a laser emitting element, scans the laser light L with a rotating mirror, and charges the surface of the photosensitive drum 1. Write the electrostatic latent image of the image in.

[Liquid developer]
The electrostatic latent image formed on the photosensitive drum 1 is developed by a liquid developer in the developing device 4. The developing apparatus 4 contains a liquid developer in which granular toner as a dispersoid is dispersed in a carrier liquid as a dispersion medium, and the developing apparatus 4 develops using the liquid developer. The toner is a resin toner containing a colorant and a binder as main components, to which a charging aid and the like are added. The toner is formed, for example, having an average particle size of 0.1 to 2 μm. On the other hand, the carrier liquid is, for example, a high resistance and low dielectric constant non-volatile liquid having a volume resistivity of 1E + 9Ω · cm or more, a relative permittivity of 10 or less, and a viscosity adjusted to 0.1 to 100 cP. As the carrier liquid, one containing an insulating solvent such as silicone oil, mineral oil, and Isopar M (registered trademark, manufactured by Exxon Co., Ltd.) as a main component and, if necessary, a charge control agent or the like can be used. Further, as long as it is within the above-mentioned range of physical property values, a liquid monomer that is cured by ultraviolet rays can also be used. In this embodiment, a liquid developer in which the mass percent concentration of toner is adjusted to 1 to 15% is used.

[Developer]
The configuration of the developing device 4 and the developing operation will be described. As shown in FIG. 2, the developing apparatus 4 as the first developing means or the second developing means includes a developing container 40 forming a casing, a developing roller 41, a squeeze roller 42, a cleaning roller 43, an electrode segment 44, and a supply tray 45. And so on.

The developing container 40 contains a liquid developer containing a monochromatic toner and a carrier liquid. As shown in FIG. 2, a part of the developing container 40 facing the photosensitive drum 1 is open, and the developing roller 41 is rotatably arranged so that a part is exposed in the opening. The developing roller 41 is formed in a cylindrical shape and is rotated in the same direction on the surface facing the photosensitive drum 1. The electrode segments 44 are arranged on the opposite side of the developing roller 41 from the photosensitive drum 1 so as to face each other with a gap of a predetermined interval (for example, 0.5 mm) from the photosensitive drum 1. A supply tray 45 is arranged below the electrode segment 44, and the liquid developer is pumped from the supply tray 45 into the above gap by the rotation of the developing roller 41. The supply tray 45 temporarily stores the liquid developer supplied from a mixer (not shown) so that the developing roller 41 can pump the liquid developer by rotation.

The electrode segment 44 forms an electric field with the developing roller 41 by applying a voltage from a power source (not shown). According to this electric field, the toner contained in the liquid developer pumped up in the gap moves toward the surface side of the developing roller 41. A squeeze roller 42 is arranged downstream of the electrode segment 44 in the rotational direction of the developing roller 41. The squeeze roller 42 abuts on the developing roller 41 to form the nip portion N1. Of the liquid developer on the developing roller 41 that has passed through the region facing the electrode segment 44, the liquid developer on the surface of the developing roller 41 that has passed through the nip portion N1 has a thickness (height in the radial direction of the developing roller). It is regulated almost uniformly. The liquid developer that has not passed through the nip portion N1 of the squeeze roller 42 flows along the upper surface of the electrode segment 44 and falls to the bottom side of the developing container 40.

The developing device 4 is rotatably provided by the developing roller contacting / detaching means 202. When the developing device 4 rotates, the developing roller 41 comes into contact with the photosensitive drum 1 at a predetermined pressure to supply the liquid developer, and the position farther from the photosensitive drum 1 than the position where the liquid developer can be supplied. Move between. When the liquid developer that has passed through the nip portion N1 of the squeeze roller 42 is conveyed to the developing position c, the electrostatic latent image on the photosensitive drum 1 is developed into a toner image. That is, the carrier liquid of the liquid developer conveyed to the developing position c by the developing roller 41 is conveyed to the developing roller 41 and the photosensitive drum 1 and separated into the developing roller side and the photosensitive drum side, so that the carrier liquid is placed on the drum. Layers are formed. Then, the toner in the liquid developer conveyed to the developing position c is selectively adhered through the carrier liquid layer in response to the electrostatic latent image formed on the photosensitive drum 1 by the electric field due to the developing voltage. In this way, the electrostatic latent image on the photosensitive drum 1 is developed into a toner image. The developing position c is a developing nip portion N2 formed by the developing roller 41 and the photosensitive drum 1.

A cleaning roller 43 is arranged on the downstream side of the developing roller 41 in the rotational direction with respect to the developing nip portion N2. The cleaning roller 43 collects the toner remaining on the developing roller 41 after passing through the developing nip portion N2, and collects the carrier liquid remaining on the developing roller 41 by applying pressure at the nip portion N3. The toner and carrier liquid collected by the cleaning roller 43 fall to the bottom side of the developing container 40. The toner and carrier liquid that have fallen to the bottom side of the developing container 40 are mixed with the liquid developer that has not passed through the nip portion N1 and returned to a mixer (not shown). Therefore, the developing container 40 is provided with a discharge port 47 communicating with the mixer, from which the liquid developer is discharged.

Returning to the description of the image forming unit P, the toner image formed on the photosensitive drum 1 is sequentially superposed on the belt at the primary transfer position d and primary transferred. A primary transfer roller 92 is provided on the inner peripheral surface side of the belt 91 so as to face the photosensitive drum 1 with the belt 91 interposed therebetween. The primary transfer roller 92 is formed of, for example, a conductive sponge, and presses the belt 91 to form a primary transfer nip portion T1 between the photosensitive drum 1 and the belt 91. The primary transfer position d is the primary transfer nip portion T1. When a primary transfer voltage is applied to the primary transfer roller 92 by a power source (not shown), the primary transfer of the toner image from the photosensitive drum 1 to the belt 91 is performed at the primary transfer position d. Further, since the carrier liquid of the carrier liquid layer on the drum surface conveyed to the primary transfer position d is divided into the photosensitive drum side and the belt side and conveyed to the photosensitive drum 1 and the belt 91, the outer peripheral surface side of the belt 91 That is, a carrier liquid layer is also formed on the surface side. In this way, at the primary transfer position d, the carrier liquid layer is also formed on the belt 91, so that the toner image can be transferred through the carrier liquid layer.

The primary transfer residual toner remaining on the drum surface without being transferred to the belt 91 at the primary transfer position d is removed by the drum cleaning device 7. The drum cleaning device 7 has a cleaning blade 70 that comes into contact with the photosensitive drum 1 at a predetermined pressure.

Returning to FIG. 1, the belt 91 is stretched over a tension roller 94, a drive roller 95, a secondary transfer inner roller 96, and a driven roller 97 arranged on the inner peripheral surface side of the belt 91. The tension roller 94 maintains the tension of the belt 91 substantially constant by applying a force for pushing the belt 91 from the inside to the outside by a pressurizing means (not shown). The drive roller 95 moves the belt 91 in the direction of arrow R2 in the drawing. The secondary transfer inner roller 96 forms the secondary transfer portion T2 with the secondary transfer outer roller 10 arranged at positions facing each other with the belt 91 interposed therebetween. The driven roller 97 is arranged between the tension roller 94 and the secondary transfer inner roller 96 with respect to the moving direction of the belt 91, and rotates in accordance with the moving belt 91.

The toner images that are sequentially superimposed on the belt and primary-transferred are collectively secondary-transferred onto the recording material S that has been conveyed to the secondary transfer unit T2. The secondary transfer portion T2 is a toner image transfer nip portion to the recording material S formed by abutting the secondary transfer outer roller 10 against the belt 91 stretched on the secondary transfer inner roller 96. In the secondary transfer unit T2, a toner image is secondarily transferred from the belt 91 to the recording material S by applying a secondary transfer voltage to the secondary transfer outer roller 10 as a transfer means by a power source (not shown). Then, the secondary transfer residual toner remaining on the belt after the secondary transfer is collected by the belt cleaning device 11.

As the belt 91 described above, a resin belt, a belt in which an elastic layer is formed on a resin base layer, or the like can be preferably used.

[Liquid volume adjuster]
As shown in FIG. 1, the image forming apparatus 100 of this embodiment includes a liquid amount adjusting apparatus 170. The liquid amount adjusting device 170 as a supply means is arranged at a position facing the driven roller 97 with the belt 91 interposed therebetween. That is, the liquid amount adjusting device 170 is a belt on the downstream side in the moving direction (downstream side in the predetermined direction) of the belt 91 from the black primary transfer unit T1Bk and on the upstream side (upstream side in the predetermined direction) in the moving direction from the secondary transfer unit T2. It is arranged on the outer peripheral surface side (surface side) of 91. In the case of the present embodiment, the liquid amount adjusting device 170 has a function of supplying the carrier liquid to the belt 91 and a function of removing the carrier liquid from the belt 91, and the liquid amount of the carrier liquid of the belt 91 can be adjusted. .. The liquid amount adjusting device 170 will be described with reference to FIG.

As shown in FIG. 3, the liquid amount adjusting device 170 can be roughly divided into a transport device 180 and a supply device 190. In the case of the present embodiment, the supply device 190 is arranged on the lower side in the gravity direction on the side farther from the belt 91 than the transfer device 180. The supply device 190 includes a supply roller 191 as a second roller, a regulation blade 192, a supply roller driving means 193, a carrier liquid tank 194, and a liquid level sensor 195. The carrier liquid is stored in the carrier liquid tank 194. The carrier liquid tank 194 is connected to a carrier tank (not shown), and the carrier liquid is replenished from the carrier tank. The carrier liquid is replenished based on the detection result of the liquid level sensor 195 arranged in the carrier liquid tank 194. Specifically, when the carrier liquid in the carrier liquid tank 194 decreases until the liquid level height detected by the liquid level sensor 195 becomes a predetermined value or less, the carrier liquid is replenished. As the liquid level sensor 195, for example, the liquid level height can be detected by measuring the time from the start of irradiation of the ultrasonic waves radiated toward the liquid surface to the reflection of the irradiated ultrasonic waves on the liquid surface and returning. In addition, ultrasonic type sensors and the like are used.

The supply roller 191 has a core metal and an elastic layer formed around the core metal. The elastic layer has, for example, a volume resistivity of 1E + 8Ω · cm or less, a hardness of 30 to 50 degrees (JIS-A), a surface roughness Rz of 2 μm or less, and is formed of urethane rubber or the like. The supply roller 191 is rotatably provided in the carrier liquid tank 194 so that a part of the outer peripheral surface is immersed in the carrier liquid contained in the carrier liquid tank 194. The supply roller 191 is rotated in the direction of arrow R3 in the figure by a supply roller driving means 193 such as a motor. The supply roller 191 can support the carrier liquid by rotating. The carrier liquid carried on the supply roller 191 is regulated by the regulation blade 192 that is in contact with the supply roller 191 with a predetermined pressing force, whereby the thickness of the carrier liquid on the supply roller 191 (height in the radial direction of the supply roller 191). Is adjusted almost uniformly. The thickness of the carrier liquid after regulation is, for example, 4 to 20 μm. In this way, the supply amount per unit time is maintained at a constant amount by the rotating supply roller 191, and the carrier liquid in the carrier liquid tank 194 is supplied to the transfer device 180.

On the other hand, the transfer device 180 includes a transfer roller 181 as a first roller, a removal blade 182, a transfer roller driving means 183, and a transfer roller applied power supply 184. The transport roller 181 has, for example, a surface roughness Rz of about 0.2 to 2 μm, and is made of stainless steel (SUS alloy). The transfer roller 181 is rotated in the direction of arrow R4 in the figure by a transfer roller driving means 183 such as a motor. The rotation direction of the transport roller 181 coincides with the moving direction of the belt 91 (arrow R2 direction in the figure) on the surface facing the belt 91, and the rotation direction of the supply roller 191 on the surface facing the supply roller 191 (arrow in the figure). R3 direction). The transport roller 181 can support the carrier liquid by rotating.

The removal blade 182 abuts on the transport roller 181 and removes the carrier liquid carried on the transport roller 181 from the transport roller 181. In the case of the present embodiment, the carrier liquid remaining on the transport roller 181 after the carrier liquid is supplied to the belt 91 is removed. By removing the carrier liquid by the removal blade 182, when the carrier liquid is supplied from the supply roller 191, the thickness of the carrier liquid on the transport roller 181 (height in the radial direction of the transport roller) becomes substantially uniform. The transport roller application power supply 184 as the voltage applying means applies a voltage having the same polarity (here, negative electrode property) as the toner of the toner image transferred on the belt to the transport roller 181.

In the present embodiment, the thickness of the carrier liquid on the transport roller 181 can be adjusted substantially uniformly by using the regulation blade 192, but an Anilox roller, a roller pair, or the like is used as the regulation means instead of the regulation blade 192. You may.

The supply device 190 can be moved between the position where the supply roller 191 is in contact with the transfer roller 181 and the position where the supply roller 191 is separated from the transfer roller 181 (see FIG. 4 to be described later) by the supply device attachment / detachment means 196. Is. That is, the supply roller 191 interposed between the carrier liquid in the carrier liquid tank 194 and the transport roller 181 is located at a contact position in contact with both the carrier liquid and the transport roller 181 in the carrier liquid tank 194, and from the transport roller 181. Move between the separated positions.

On the other hand, the transfer device 180 can be moved between the position where the transfer roller 181 is in contact with the belt 91 and the position away from the belt 91 (see FIG. 8 to be described later) by the transfer device contact / detachment means 185. In the present embodiment, the operation mode (operation mode) of the liquid amount adjusting device 170 is changed into the supply mode (supply mode) and the removal mode (supply mode) by the cooperation of the supply device connection / disconnection means 196 and the transfer device connection / disconnection means 185. It is set to one of the collection modes). Here, the operation mode of the liquid amount adjusting device 170 will be described.

A supply mode, which is one of the operation modes, will be described with reference to FIG. As shown in FIG. 3, when the liquid amount adjusting device 170 is in the supply mode, the supply roller 191 abuts on the transfer roller 181 to form the nip portion N4, and the transfer roller 181 abuts on the belt 91 to form the nip portion N5. To form. The carrier liquid pumped from the carrier liquid tank 194 by the supply roller 191 is supplied from the supply roller 191 to the transfer roller 181 by the nip portion N4. In the nip portion N4, about half the amount of the carrier liquid pumped up by the supply roller 191 is moved to the transport roller side. Therefore, the thickness of the carrier liquid on the transport roller 181 is, for example, 2 to 10 μm. The transfer roller 181 conveys the carrier liquid supplied from the supply roller 191 toward the nip portion N5. The carrier liquid that has reached the nip portion N5 is divided into a belt 91 side and a transport roller 181 side. That is, the carrier liquid is supplied to the belt 91. On the other hand, the carrier liquid separated on the transport roller 181 side is removed by the removal blade 182 and collected in the carrier liquid tank 194. Since a voltage having the same polarity as the toner is applied to the transfer roller 181 by the transfer roller applied power supply 184, the toner of the toner image transferred on the belt does not move from the belt 91 to the transfer roller 181.

A removal mode, which is one of the operation modes, will be described with reference to FIG. As shown in FIG. 4, when the liquid amount adjusting device 170 is in the removing mode, the transport roller 181 abuts on the belt 91 to form the nip portion N5, while the supply roller 191 does not abut on the transport roller 181. Nip portion N4 (see FIG. 3) is not formed. That is, the transport roller 181 and the supply roller 191 are separated from each other. Therefore, the carrier liquid pumped from the carrier liquid tank 194 by the supply roller 191 is not supplied to the transport roller 181. If the carrier liquid in the carrier liquid tank 194 is not supplied to the transport roller 181, the carrier liquid is not supplied to the belt 91. However, the carrier liquid is supplied from the belt 91 at the nip portion N5 to the transport roller 181 to which the carrier liquid is not supplied. This is because when the carrier liquid of the carrier liquid layer formed on the belt 91 reaches the nip portion N5, it is separated into the belt side and the transport roller side. As a result, a part of the carrier liquid in the carrier liquid layer formed on the belt 91 is removed from the belt 91 by the transport roller 181. As described above, in the present embodiment, the carrier liquid in the carrier liquid tank 194 is not supported on the transport roller 181 so that the carrier liquid can be removed from the belt 91 by the transport roller 181.

The carrier liquid removed from the belt 91 by the transport roller 181 is removed from the transport roller 181 by the removal blade 182 and collected in the carrier liquid tank 194. Further, in the removal mode as in the supply mode described above, since the voltage of the same polarity as the toner is applied to the transport roller 181 by the transport roller applied power supply 184, the toner of the toner image transferred on the belt is the belt. It does not move from 91 to the transfer roller 181.

[Control unit]
As shown in FIG. 1, the image forming apparatus 100 of this embodiment includes a control unit 200. The control unit 200 will be described with reference to FIGS. 1 and 2 with reference to FIG. In addition to the illustrations, various devices such as a motor and a power supply for operating the image forming apparatus 100 are connected to the control unit 200, but the illustration and description thereof are omitted here because it is not the main purpose of the invention. ..

The control unit 200 as a control means performs various controls of the image forming apparatus 100 such as an image forming operation, and has a CPU (Central Processing Unit) (not shown). A memory 201 such as a ROM or RAM or a hard disk device as a storage means is connected to the control unit 200. Various programs, data, and the like for controlling the image forming apparatus 100 are stored in the memory 201. The control unit 200 may execute the image forming job stored in the memory 201 to operate the image forming apparatus 100 to perform the image forming. In the case of the present embodiment, the control unit 200 adjusts the liquid amount of the carrier liquid layer formed on the belt 91 during the execution of the image forming job. The liquid amount adjustment of this carrier liquid layer will be described later. Note that the memory 201 can temporarily store the calculation processing results and the like associated with the execution of various control programs.

The image forming job is a series of operations from the start of image formation to the completion of the image forming operation based on the print signal for forming an image on the recording material. That is, after starting the preliminary operation (so-called forward rotation) required for performing image formation, the preliminary operation (so-called backward rotation) required for ending image formation is completed through the image forming step. It is a series of operations up to. Specifically, it refers to the period from the front rotation (preparatory operation before image formation) after receiving the print signal (reception of the image formation job) to the rear rotation (operation after image formation), and the image formation period. , Including between papers. In the present specification, the term “pre-rotation” means that the photosensitive drums 1Y to 1Bk are started to rotate without forming a toner image by receiving a print signal at the start of image formation, and then the photosensitive drums 1Y to 1Bk are started. This is the period until the exposure is started. The post-rotation period is a period from the end of the final image formation of the image forming job until the rotation of the photosensitive drums 1Y to 1Bk, the belt 91, etc., which are continuously rotated without forming a toner image, is stopped.

In addition to the memory 201, the control unit 200 is connected to the developing roller attachment / detachment means 202 via an interface (not shown). The developing roller attachment / detachment means 202 is a motor, an operating mechanism, or the like that rotates the developing apparatus 4. As the developing device 4 is rotated, the developing roller 41 is switched between a state in which the developing roller 41 is in contact with the photosensitive drum 1 and a state in which the developing roller 41 is separated from the photosensitive drum 1. The developing device 4 is switched to a state of being separated from the photosensitive drum 1 during the post-rotation of the image forming job and a state of being in contact with the photosensitive drum 1 during the pre-rotation of the image forming job.

Further, the control unit 200 is connected to the transfer roller drive means 183, the supply roller drive means 193, the transfer device attachment / detachment means 185, the supply device attachment / detachment means 196, the transfer roller applied power supply 184, and the like. As described above, the transfer roller driving means 183 is a motor or the like that rotates the transfer roller 181. The supply roller driving means 193 is a motor or the like that rotates the supply roller 191. It is preferable that the transport roller 181 and the supply roller 191 are rotated at the peripheral speed of the drive roller 95, that is, at the same peripheral speed as the moving speed of the belt 91. The transfer device attachment / detachment means 185 is a motor, an operation mechanism, or the like that moves the transfer device 180 so as to move between the position where the transfer roller 181 is in contact with the belt 91 and the position away from the belt 91. The supply device attachment / detachment means 196 is a motor, an operation mechanism, or the like that moves the supply device 190 so as to move between the position where the supply roller 191 comes into contact with the transfer roller 181 and the position away from the transfer roller 181. be. The transfer roller applied power supply 184 is a power source that applies a voltage having the same polarity as the toner to the transfer roller 181.

By the way, when the image forming job is executed, the control unit 200 makes various settings for operating the image forming apparatus 100 based on the print setting information included in the print signal received from the external host apparatus (not shown). The print setting information includes information such as designation of an image formation mode, type and size of recording material S, and designation of a paper cassette (not shown) accommodating recording material S. In the case of the present embodiment, the control unit 200 can set the operation mode of the liquid amount adjusting device 170 based on the designation of the image formation mode. Specifically, the supply mode (see FIG. 3) is set in the monochrome mode (second mode), and the removal mode (see FIG. 4) is set in the full color mode (first mode).

Hereinafter, the liquid amount adjustment control of the present embodiment will be described in detail with reference to FIGS. 1 to 3 with reference to FIGS. 6 to 7 (b). FIG. 6 shows the liquid amount adjustment control of the present embodiment. The control unit 200 starts the liquid amount adjustment control shown in FIG. 6 in accordance with the execution of the image forming job.

As shown in FIG. 6, the control unit 200 acquires print setting information from the received print signal (S1). The control unit 200 determines whether or not the designation of the image formation mode of the acquired print setting information is the "full color mode" (S2). In the "full color mode" (YES in S2), the control unit 200 brings the developing roller 41 into contact with the photosensitive drum 1 in all the image forming units PY to PBk (S3). Then, the control unit 200 sets the operation mode of the liquid amount adjusting device 170 to the above-mentioned "removal mode" (see FIG. 4) (S4). After setting the liquid amount adjusting device 170 to the "removal mode", the control unit 200 starts the image forming operation.

On the other hand, when the designation of the image forming mode is not "full color mode" but "monochrome mode" (NO in S2), the control unit 200 brings the developing roller 41 into contact with the photosensitive drum 1 only in the black image forming unit PBk. (S5). Then, the control unit 200 sets the operation mode of the liquid amount adjusting device 170 to the above-mentioned “supply mode” (see FIG. 3) (S6). After setting the liquid amount adjusting device 170 to the "supply mode", the control unit 200 starts the image forming operation.

FIG. 7A shows a change in the amount of the carrier liquid layer in the full color mode. FIG. 7A shows the thickness of the carrier liquid layer at the time of passing through the primary transfer portions T1Y to T1Bk of yellow, magenta, cyan, and black, and at the time of reaching the secondary transfer portion T2. When the developing roller 41 comes into contact with the photosensitive drum 1Y in each of the image forming portions PY to PBk, the carrier liquid is supplied to the photosensitive drums 1Y to 1Bk. The carrier liquid supplied to the photosensitive drums 1Y to 1Bk is supplied to the belt 91 by being separated on the belt side by the primary transfer portions T1Y to T1Bk as described above. Therefore, the amount of the carrier liquid layer formed on the belt 91 gradually increases toward the downstream side in the moving direction, and as a result, as shown in FIG. 7A, the thickness of the carrier liquid layer is the primary transfer of black. It becomes maximum when it passes through the part T1Bk. Thus, in the full color mode, excess carriers in the carrier liquid layer are likely to occur.

As described above, in the present embodiment, in order to eliminate the excess carrier, the control unit 200 sets the operation mode of the liquid amount adjusting device 170 to the “removal mode”, and the liquid amount adjusting device 170 is charged with a predetermined amount from the carrier liquid layer. Remove the carrier liquid. By doing so, as shown in FIG. 7A, the amount of liquid in the carrier liquid layer at the time of reaching the secondary transfer portion is suppressed to an appropriate amount, so that fixing failure in the fixing device 13 due to excessive carriers Does not occur. In addition, transfer defects in the secondary transfer unit T2 due to carrier shortage do not occur.

FIG. 7B shows the change in the amount of the carrier liquid layer in the monochrome mode. FIG. 7B also shows the thickness of the carrier liquid layer at the time of passing through each of the primary transfer portions T1Y to T1Bk and at the time of reaching the secondary transfer portion T2. However, as can be understood in comparison with FIG. 7A, the thickness of the carrier liquid layer is “0” in the primary transfer portions T1Y to T1C other than black. In the monochrome mode, the developing roller 41 is brought into contact with the photosensitive drum 1Y only in the black image forming portion PBk, and the developing roller 41 is separated from the photosensitive drums 1Y to 1C in the other image forming portions PY to PC. Because it is. In this case, the carrier liquid is not supplied from the photosensitive drums 1Y to 1C to the belt 91 in the primary transfer portions T1Y to T1C other than black, and the carrier liquid is supplied from the photosensitive drum 1Bk to the belt 91 only by the black primary transfer portion T1Bk. .. Therefore, since the carrier liquid layer is formed only when it passes through the black primary transfer portion T1Bk, the thickness of the carrier liquid layer becomes "0" in the primary transfer portions T1Y to T1C other than black. The amount of the carrier liquid layer formed in the monochrome mode is substantially equal to the amount of the carrier liquid layer at the time of passing through the primary transfer unit T1Y in the full color mode.

In the monochrome mode, since the carrier liquid layer is formed only when the carrier liquid layer passes through the primary transfer unit T1Bk, the liquid amount of the carrier liquid layer tends to be less than the appropriate amount and the carrier is deficient. In order to solve this carrier shortage, the control unit 200 sets the operation mode of the liquid amount adjusting device 170 to the "supply mode", and causes the liquid amount adjusting device 170 to supply the carrier liquid to the belt 91. As a result, the amount of liquid in the carrier liquid layer at the time of reaching the secondary transfer unit T2 increases to an appropriate amount, so that transfer defects in the secondary transfer unit T2 due to carrier shortage do not occur. In addition, fixing failure in the fixing device 13 due to excessive carriers does not occur.

As described above, in the present embodiment, the operation mode of the liquid amount adjusting device 170 is set according to the image formation mode. The liquid amount adjusting device 170 supplies the carrier liquid to the belt 91 by being set to the supply mode (see FIG. 3) in the monochrome mode. That is, in the monochrome mode in which the carrier liquid layer is relatively prone to carrier shortage, the carrier liquid is supplied to the carrier liquid layer, so that the carrier shortage can be solved. On the other hand, the liquid amount adjusting device 170 removes the carrier liquid from the belt 91 by setting the removal mode (see FIG. 4) in the full color mode. That is, in the full color mode in which the carrier liquid layer is relatively likely to have a carrier excess, the carrier liquid is removed from the carrier liquid layer, so that the carrier excess can be eliminated. By adjusting the amount of the carrier liquid layer according to the image formation mode in this way, transfer defects occur due to carrier shortage in monochrome mode, and fixing defects occur due to carrier excess in full color mode. Is suppressed.

<Other Embodiments>
By the way, in the above-described embodiment, the operation mode of the liquid amount adjusting device 170 is set to the removal mode in the full color mode and the supply mode in the monochrome mode. The combination of operation modes is not limited to this. For example, it may be a combination of operation modes as shown in Table 1 below. In Table 1, "supply" indicates a supply mode, "removal" indicates a removal mode, and "normal" indicates a normal mode.

FIG. 8 shows a normal mode which is one of the operation modes. As shown in FIG. 8, when the liquid amount adjusting device 170 is in the normal mode, the supply roller 191 contacts the transport roller 181 to form the nip portion N4, while the transport roller 181 does not contact the belt 91. Nip portion N5 (see FIG. 3) is not formed. That is, the belt 91 and the liquid amount adjusting device 170 are separated from each other. Therefore, even if the carrier liquid is pumped up from the carrier liquid tank 194 by the supply roller 191 and supplied to the transport roller 181, the carrier liquid is not supplied to the belt 91. Further, the carrier liquid of the carrier liquid layer formed on the belt 91 is not removed from the belt 91.

As shown in Table 1, the operation mode of the liquid amount adjusting device 170 may be set to the removal mode in the full color mode and the normal mode in the monochrome mode. This combination of operation modes is effective when the recording material S has little penetration of the carrier liquid such as a plastic film or coated paper. That is, when the permeation of the carrier liquid into the recording material S is small and the amount of the carrier liquid layer formed on the belt 91 is large, fixing defects due to excessive carriers are more likely to occur. Therefore, in the full color mode in which the amount of liquid in the carrier liquid layer is relatively large, the liquid amount adjusting device 170 removes the carrier liquid from the belt 91. On the other hand, in the monochrome mode in which the amount of the carrier liquid layer is relatively small, even if the carrier liquid is not supplied to the belt 91, the carrier liquid permeates the recording material S so little that the transfer is caused by the carrier shortage. Defects are unlikely to occur. Therefore, in the monochrome mode, it may be set to the normal mode.

Alternatively, as shown in Table 1, the operation mode of the liquid amount adjusting device 170 may be set to the normal mode in the full color mode and the supply mode in the monochrome mode. This combination of operation modes is effective when the recording material S has a large penetration of the carrier liquid such as plain paper or recycled paper. That is, when the carrier liquid permeates into the recording material S is large, if the amount of the carrier liquid layer formed on the belt 91 is small, transfer defects due to carrier shortage are more likely to occur. Therefore, in the monochrome mode in which the amount of liquid in the carrier liquid layer is relatively small, the liquid amount adjusting device 170 supplies the carrier liquid to the belt 91. On the other hand, in the full color mode in which the amount of the carrier liquid layer is relatively large, even if the carrier liquid is not removed from the belt 91, the carrier liquid permeates the recording material S so much that the fixing failure due to the excess carrier occurs. Hard to occur. Therefore, in the full color mode, it may be set to the normal mode.

In the above-described embodiment, the liquid amount adjusting device 170 having the transport device 180 and the supply device 190 is shown, but the liquid amount adjusting device 170 is not limited to this. For example, as shown in FIG. 9, the liquid amount of the carrier liquid layer may be adjusted by using only the supply device 190 without using the transfer device 180 (see FIG. 3). In this case, since the supply roller 191 is brought into contact with the belt 91 without going through the transfer roller 181 (see FIG. 3), the carrier liquid of the carrier liquid tank 194 can be directly supplied from the supply roller 191 to the belt 91. Then, the carrier liquid tank 194 is moved to a position where it does not come into contact with the supply roller 191 so that the supply roller 191 can remove the carrier liquid from the belt 91.

In the case of the present embodiment, the amount of the carrier liquid supplied to the belt 91 may be adjusted by rotating the transport roller 181 and the supply roller 191 with a peripheral speed difference. For example, when increasing the supply amount of the carrier liquid, the supply roller 191 may be rotated faster than the transport roller rotated at the same speed as the belt 91. However, it is preferable that the transport roller 181 and the supply roller 191 are rotated with a speed difference of 5% or less.

In the above-described embodiment, the developing device 4 is separated from the photosensitive drum 1 in the monochrome mode so that the liquid developer is not supplied to the belt 91 from the photosensitive drum other than black, but the present invention is not limited to this. For example, a photosensitive drum 1 other than black may be provided so as to be in contact with and detachable from the belt 91, and may be brought into contact with the belt 91 in the full color mode and separated from the belt 91 in the monochrome mode.

In the above-described embodiment, the configuration in which the intermediate transfer belt is used as the intermediate transfer body has been described, but the intermediate transfer body may be, for example, an intermediate transfer drum formed in a drum shape.

1Y to 1Bk ... 1st image carrier (second image carrier, photosensitive drum), 4Y to 4Bk ... 1st developing means (second developing means, developing device), 10 ... Transfer means (secondary transfer outer roller) ), 91 ... Intermediate transfer body (intermediate transfer belt), 100 ... Image forming apparatus, 170 ... Supply means (liquid amount adjusting device), 181 ... First roller (conveying roller), 184 ... Voltage applying means (conveying roller applied power supply), 191 ... Second roller (supply roller), 194 ... Carrier liquid tank, 200 ... Control means (control unit), S ... Recording material

Claims (4)

The first image carrier on which the electrostatic latent image is formed, and
A second image carrier on which an electrostatic latent image is formed,
A first developing means for developing an electrostatic latent image formed on the first image carrier with a liquid developer containing toner and a carrier liquid.
A second developing means for developing an electrostatic latent image formed on the second image carrier with a liquid developer containing toner and a carrier liquid.
An intermediate transfer body in which a toner image is primarily transferred from the first image carrier and the second image carrier as the carrier liquid moves.
A transfer means for secondary transfer of the toner image primary transferred to the intermediate transfer body to a recording material, and
The first mode in which the toner image is primarily transferred along with the movement of the carrier liquid from the first image carrier and the second image carrier to the intermediate transfer body, and the carrier liquid from the first developing means to the first image carrier. A control means capable of selectively executing a second mode in which the first developing means is controlled so that the second image is not supplied, and the toner image is primarily transferred along with the movement of the carrier liquid from the second image carrier to the intermediate transfer body. When,
The intermediate transfer body is arranged on the downstream side of the second image carrier and on the upstream side of the transfer means so as to face the intermediate transfer body in the moving direction of the intermediate transfer body, and is placed on the intermediate transfer body at least in the second mode. for example Bei and a supply means capable of supplying the carrier liquid,
The supply means can recover the carrier liquid from the intermediate transfer body, and the supply means can recover the carrier liquid.
The control means can selectively execute a recovery mode in which the carrier liquid is recovered from the intermediate transfer body by the supply means and a supply mode in which the carrier liquid is supplied to the intermediate transfer body by the supply means.
An image forming apparatus characterized in that. The supply means has a carrier liquid tank for accommodating the carrier liquid, and a first roller which is in contact with the intermediate transfer body and can support the carrier liquid contained in the carrier liquid tank.
The control means supplies the carrier liquid to the intermediate transfer body by supporting the carrier liquid of the carrier liquid tank on the first roller in the second mode, and the carrier of the carrier liquid tank in the first mode. By not supporting the liquid on the first roller, the carrier liquid is recovered from the intermediate transfer body by the first roller.
The image forming apparatus according to claim 1. The supply means is provided so as to be detachable from the first roller, and has a second roller capable of supplying the carrier liquid of the carrier liquid tank to the first roller.
In the second mode, the control means brings the second roller into contact with the first roller to supply the carrier liquid of the carrier liquid tank from the second roller to the first roller, and the first roller. By separating the second roller from the first roller in the mode, the supply of the carrier liquid in the carrier liquid tank from the second roller to the first roller is stopped.
The image forming apparatus according to claim 2. A voltage applying means for applying a voltage having the same polarity as the toner is provided on the first roller.
The image forming apparatus according to claim 2 or 3.

Images